<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .float {
        float: left;
        }
        #main {
        width: 100%;
        height: 200px;
        background-color: lightpink;
        }
        #main-wrap {
        margin: 0 190px 0 190px;
        }
        #left {
        width: 190px;
        height: 200px;
        background-color: lightsalmon;
        margin-left: -100%;
        }
        #right {
        width: 190px;
        height: 200px;
        background-color: lightskyblue;
        margin-left: -190px;
        }
    </style>
</head>
<body>
    <div id="main" class="float">
        <div id="main-wrap">main</div>
    </div>
    <div id="left" class="float">left</div>
    <div id="right" class="float">right</div>
</body>
</html>